1. Field of Invention
The present invention relates to the field of marine seismic data acquisition systems and methods of using same. More specifically, the invention relates to systems and methods for selecting receivers on seismic streamers to use during a seismic data survey.
2. Related Art
Marine seismic exploration investigates the structure and character of subsurface strata under a body of water. In order to economically gather marine seismic data for large survey areas, one or more seismic vessels in a fleet may tow one or more seismic sources and multiple seismic streamer cables through the water. Streamers typically vary in length between three and twelve kilometers. Receivers are positioned along each streamer. The in-line interval between each receiver may range from about 3 and 25 meters, with 12.5 meters comprising typical interval spacing, although this spacing is tending to become less as clients demand more and higher quality data. Recent marine seismic surveys may employ receivers about 3 meters apart. Despite the best efforts of streamer and vessel steering devices and sometimes complicated computer algorithms, external forces, such as winds, tides, ocean currents, and the like, may affect the position of streamers and receivers. The term “skew” is sometimes used to describe a streamer or receiver following a non-desired path, possibly due to one or more external forces. One type of skew is “inline skew”, which may be explained as a streamer positioned forward or aft of its desired position, although generally inline. If a particular streamer of a towed spread is fore or aft of its neighbor, the data may not be entirely acceptable, even though an identical configuration in terms of number of streamers, number of receivers, and even inline path, is followed. The problem is compounded, of course, if more than one streamer is experiencing inline skew.
From the above it is evident that there is a need for correcting for inline skew of towed seismic streamers.